This invention relates to novel silylorganosulfonates and their use in the stabilization of aqueous silicates.
Aqueous silicates as a class of compounds can take a role as useful materials, or they can in some circumstances be considered to be nuisances. For example, silicates are purposely added to antifreeze compositions as corrosion inhibitors, while certain silicates occurring in other kinds of heat transfer systems cause many problems by precipitating from solution and depositing on the interior surfaces of the heat transfer system which causes a reduction in efficiency.
For a long time, it has been a goal of the automotive antifreeze producers to find an efficient, low-cost method of maintaining the silicate corrosion inhibitors in solution; likewise, it has been a goal of engineers to find some method by which the naturally occurring soluble silicates could be maintained in solution so as to prevent their buildup on the interior surfaces of the heat transfer systems, and thus enhance the efficiency of the heat transfer systems. There have been many efforts therefore to stabilize silicates so that they could be more persistent in their corrosion inhibiting properties.
Arthur N. Pines et al. in U.S. Pat. Nos. 3,312,622 and 3,198,820 describe combinations of silicone-silicate polymers as corrosion inhibitors. Although the patent does not specifically describe the stabilization of silicates, it is very obvious from the specification that the so-called "novel organosilicon polymer" does, in fact, contribute to the persistency of the corrosion inhibition of the silicone-silicate polymers of that invention. The novelty, as pointed out therein, is the use of silyl carboxylates in conjunction with the silicates. Such materials are discussed as enhancing the corrosion inhibition of common antifreeze compositions and overcome disadvantages of other prior art corrosion inhibitors such as handling and dispensing of the antifreezes; selective corrosion inhibition of certain metals, poor shelf life, tendency to attack rubber hoses, excessive foaming in use and the causing of alcohols to decompose.
In later issued patents, U.S. Pat. Nos. 3,341,469 and 3,337,496, Pines et al. describe another system that was found useful for inhibiting corrosion in aqueous alcohol compositions. It consisted of a mixture of an alkyl silsesquioxane, a siloxane modified with a cyanoalkyl or carbinol group, and a silicate. These materials are stated as being "remarkably soluble in aqueous liquids". Further, the compositions are alleged to overcome many of the above-mentioned disadvantages.
U.S. Pat. No. 3,948,964, issued Apr. 6, 1976, describes the stabilization of partially hydrolyzed silicic acid esters using stabilizers selected from organic compounds such as cyclic ethers, ether alcohols, carboxylic acid esters and ketones. Such stabilized materials are described as binders for zinc dust pigments and the like.
U.S. Pat. No. 4,333,843, issued June 8, 1982, and U.S. Pat. No. 4,370,255, issued Jan. 25, 1983, describe gellation resistant aqueous glycol compositions useful as antifreezes, which glycol compositions contain an organophosphorus-silicon compound to stabilize the silicates in the composition and act as a corrosion inhibitor for metals with which the compositions come in contact.
In a recent publication, E. Plueddemann, Silane Coupling Agents, 62-72 (1982), it was reported that sodium siliconate silylpropylsulfonate, NaO.sub.3/2 SiCH.sub.2 CH.sub.2 CH.sub.2 SO.sub.3 Na, was marginally active in stabilizing silicate solutions against gelling. The silicate stabilizing effect of sulfonate functional silicate, however, was described as poor in comparison with phosphonate functional siliconate. U.S. Pat. No. 4,354,002, issued Oct. 12, 1982, claims copolymers of silicate and aliphatic silicone sulfonates as corrosion inhibitors of improved stability. Useful silicone compounds described in this patent have a sulfonate group attached to silicon by an aliphatic hydrocarbon unit and are represented by the siliconate silylpropylsulfonate also reported in the above publication by E. Plueddemann. U.S. Pat. No. 4,352,742, issued Oct. 5, 1982, claims corrosion inhibitors that are copolymers of silicate and a somewhat different sulfonate functional silicon compound. In the copolymers of this patent, the sulfonate group is attached to silicon by an aliphatic hydroxy-substituted group in which the hydroxy substituent is bonded to a carbon atom adjacent to the carbon atom to which the sulfonate group is attached. U.S. Pat. No. 4,362,644, issued Dec. 7, 1982, claims corrosion inhibitors that are copolymers of silicate and sulfonate functional silicones. In the copolymers of this patent, the sulfonate group is bonded to an aryl group and the aryl group is attached to silicon via a 2 to 4 carbon alkylene bridge.
Bailey discloses in U.S. Pat. No. 2,968,643 sulfo-aralkylsilicon compounds for use in the form of their sulfonate salts as anti-fog agents for glass surfaces. Beta-(sulfophenyl)ethyl polysiloxane, HO.sub.3 SC.sub.6 H.sub.4 -CH.sub.2 CH.sub.2 SiO.sub.3/2, is representative of the compounds disclosed by Bailey. Haluska discloses in U.S. Pat. No. 3,328,449 sulfopropylated organofunctional silanes and siloxanes that are useful as detergents, ion exchange resins, wetting agents, antistat agents for synthetic fibers, and polymerization catalyst for siloxanes. The silane, (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.3 NH(CH.sub.2).sub.2 NH(CH.sub.2).sub.3 SO.sub.3 H, is representative of the compounds disclosed by Haluska.
None of the above references, however, describe the siliconate compositions of the instant invention. The advantages of the prior art methods can be obtained with the instant invention and additional advantages over the prior art are obtained by this invention. Most notable are the advantages of low cost, enhanced effectiveness in stabilization of silicates and the persistency of corrosion inhibition.